1. Field of the Invention
The present invention relates generally to a mobile communication terminal, and more particularly to a transmitter that reduces electrical power consumption in a mobile communication terminal.
2. Description of the Related Art
Commonly, mobile communication terminals are driven by rechargeable batteries in order to secure their mobility. Further, the operation time of mobile communication terminals is determined according to the charge capacity of such rechargeable batteries. Mobile communication terminals have various functions and consume quantities of electric power while driving a plurality of elements according to these various functions. Accordingly, this causes a large limitation in the use of mobile communication terminals, as the batteries of mobile communication terminals must be frequently charged. Therefore, battery-related technologies have been developed, such that many batteries having charge capacities larger than those of previous batteries have come into the market. In addition to such technology for increasing the charge capacity of a battery, technology for saving the power of a battery by minimizing the power consumption in a mobile communication terminal has been continuously developed.
FIG. 1 is a block diagram illustrating a transmitter capable of reducing the power consumption in a conventional mobile communication terminal, and FIG. 2 is a view illustrating an operation of the transmitter in FIG. 1. Referring to FIG. 1, the transmitter includes a modem 10, a transmission signal processor 12, and a local oscillator device 14. The modem 10 converts a voice signal input through a microphone into a digital signal and provides the transmission signal processor 12 with the digital signal. The transmission signal processor 12 modulates the digital signal from the modem 10 into a radio signal and outputs the radio signal.
The transmission signal processor 12 in the mobile communication terminal enters an idle mode, a transmission mode, or a puncture mode according to operation states. In the idle mode, the terminal performs only a reception operation without performing a transmission operation, i.e., the transmission signal processor 12 is in a disabled state. In the transmission mode, the terminal performs both a transmission operation and a reception operation, i.e., the transmission signal processor 12 is in an enabled state. In the puncture mode, some elements of the transmission signal processor 12 are in an off state in order to reduce power consumption in the terminal when the terminal performs both a transmission operation and a reception operation and there exist no transmission data for a predetermined time period.
In the transmission mode, the transmission signal processor 12 is enabled and operates normally. That is, the transmission signal processor 12 is in an enabled state by a control signal from the modem 10. FIG. 2 illustrates a timing of the control signal Tx_ON. In FIG. 2, the control signal enables the transmission signal processor 12 in its high state and disables the transmission signal processor 12 in its low state. When a user communicates using the terminal, the transmission signal processor 12 is enabled to modulate a data signal input from the modem 10 into a radio signal. Because the modem 10 is connected to the microphone, existence or absence of a data signal to be transmitted can be understood.
Accordingly, when a voice signal is not input from a user even though the transmission signal processor 12 is in a transmission mode, the modem 10 causes the control signal to be in a low state. As a result, the transmission signal processor 12 is disabled. Herein, the transmission signal processor 12 is switched into the puncture mode.
When the control signal from the modem 10 is in a high state, the transmission signal processor 12 is switched into the transmission mode and processes a voice signal to be transmitted. The local oscillator device 14 provides a local oscillator signal to the transmission signal processor 12 and includes a voltage controlled oscillator (VCO), a phase locked loop (PLL), etc., in order to generate the local oscillator signal.
Additionally, FIG. 2 illustrates an on/off process of the transmission signal processor 12 and the local oscillator device 14 over time when the transmission signal processor 12 is switched from a puncture mode to a transmission mode. When the control signal applied from the modem 10 is in a high state, the transmission signal processor 12 and all elements of the local oscillator device 14 operate. Further, the modem 10 provides a high signal to the transmission signal processor 12, considers a time period for which all elements of the local oscillator device 14 are stabilized, and then provides the transmission signal processor 12 with data signals (I signal and Q signal) to be transmitted (Tx-I/Q). However, when the control signal applied from the modem 10 is in a low state, the transmission signal processor 12 is disabled, but the local oscillator device 14 maintains an enabled state (Tx PLL, VCO) because each element included in the local oscillator device 14 requires a time period for operation stabilization, and the local oscillator device 14 always maintains a current state when the transmission signal processor 12 enters a puncture mode. Accordingly, when the data signals to be transmitted from the modem 10 are not provided to the transmission signal processor 12, the transmission signal processor 12 enters a puncture mode and is disabled. Consequently, power consumption can be reduced.
However, in the conventional transmitter as described above, because the local oscillator device 14, including the VCO, the PLL, etc., is not disabled when the transmission signal processor 12 is in a puncture mode, power consumed by the local oscillator device 14 cannot be further reduced.